Have you figured out how the Philippines Vietnam and Japan have already made an alliance, and did you figure out which ones called on the US for Assurances.
Now have you figured out what the Chinese have done with their own actions to cause a problem wherein it affects others outside that region.....as well as other nations in that region. Its really not that hard with any understanding.
The United States should avoid inadvertently encouraging the claimants to engage in confrontational behavior. For example, Secretary of State Hillary Clinton's reference in November 2011 to the South China Sea as the West Philippine Sea could have unintended consequences such as emboldening Manila to antagonize China rather than it seeking to peacefully settle their differences.
Armed Clash in the South China Sea - Council on Foreign Relations
Killing one person is murder, killing 100,000 is foreign policy
According to what I recall from my college days spent studying history (which is by no means cast in concrete ), China has claimed ownership of the Sprattlys since the 1800s. At the end of WW2, Japan "returned" the Sprattlys to China, with French backing and allied approval. China's move now is unusual, but it's been rumored for quite a while that this might be coming. Is this a "triple Dog dare you" message to the US, and is this really all up to us? It seems more a matter for the UN, IMO. Interesting....